In mammalian fertilization, one important site of sperm-egg interaction occurs on the surface of the zona pellucida (ZP). The ZP is an extracellular matrix specific to mature mammalian oocytes. Sperm must first attach to and penetrate the ZP prior to actual fertilization of the egg. Specific receptors for sperm-ZP recognition are believed to reside on each gamete. Human sperm-ZP interactions will be studied by an examination of the specific sperm and ZP molecules that are directly involved in sperm-zona recognition and binding. Rabbit polyclonal antibodies will be raised against human sperm antigens which have previously been shown to have affinity for the ZP. These antibodies will be used to localize the sperm antigens on the sperm membrane by epifluorescent microscopy. Localization of the antigens on the sperm membrane will provide information on the regionalization of these antigens. The antibodies will also be used to examine whether or not they can inhibit sperm-zona interaction in vitro. Parallel studies on the human ZP will involve electrophoretic and lectin binding characteristics of the ZP molecules. Monoclonal antibodies (MAB) will be produced against solubilized human ZP and screened against the individual molecules that comprise the ZP to obtain MAB's specific for each ZP component. The MAB's will be used to examine their ability to interfere with sperm-ZP binding, and to localize regions on the human sperm which bind specific ZP components. The cross-reactivity of antiZP and anti-sperm antibodies with sperm and ZP of other mammalian species will be examined to determine if the specific molecules involved in sperm-ZP recognition are common among species. Naturally occurring anti-sperm and anti-ZP antibodies have been shown to interfere with fertilization. The identification and characterization of the specific molecules involved, therefore, may not only aid in the diagnosis of also have contraceptive potential as well.